Problem with 'pooling' at points and spheres models

[Whayt 0]

I'm fairly new to 3D printing and just getting back into it after a long break and am unable to figure out what is causing this problem.

 

I was 3D printing a little figure for fun and when it came down to the top of the sphere of the head or point on the back the filament just started to puddle up and pool. I also tried it on a model of just a pyramid.

 

I've tried decreasing the temp, flow rate, speed and even tried a different filament with no luck.

 

Hopefully one of you out there will be able to help me cause I'm over here pulling my hair out over this printer.

[gr5 2,004]

That's a common problem.  I usually solve that by printing two (or even 5) of the same object.

 

Or I print a tower right next to the part.  This allows the previous layer to cool a little while it prints the tower (or other object).  Otherwise the nozzle never leaves the puddle/blob and so it can't solidify.

 

Another solution is called "lift head".  Enable that feature and set the minimum layer time to something like 3 or 5 seconds.  Then when it gets to these tiny layers it will move the head away for a few seconds to cool.  The problem is you are just trading one problem for another - while the head is "lifted" it will slowly (over 2 seconds) extrude a tiny little sausage-string and then when it continues it will glue that into the side of the part and you get these annoying hairs.

 

I prefer the tower/2 parts solution instead.

 

[geert_2 556]

Like gr5 said: this is a cooling problem: the hot nozzle keeps sitting on same spot on top of the model, so it can't cool down and solidify. This is a limitation of this printing-concept.

 

I often print small models that have this problem. Then I print multiple at once, so one can cool while the other is printing. Or I print a dummy tower next to the real model. Ideally, the dummy should have the complementary surface area as the real model, so that the total area per layer is constant. Brutal changes in layer area show up as horizontal lines on small models.

 

Printing slow and cool also helps.

 

I am no fan of moving away the nozzle without extruding: then the filament keeps sitting in the nozzle for a longer time, and gets a different viscosity. This also shows up as horizontal deformations in the model. And the nozzle may leak while sitting and waiting aside, causing blobs.

 

A dummy tower reduces the effect, but does not eliminate it:

 

 

Theoretical model of a dummy with complementary shape:

 

 

Part of a real design:

 

 

Tiny models, each ca. 20mm high, printed at different speeds and temperatures. Printing tiny models on their back -if the model allows it - also increases layer cooling time:

 

Edited March 6, 2020 by geert_2
corrected typo

[Whayt 0]

12 hours ago, geert_2 said:

Like gr5 said: this is a cooling problem: the hot nozzle keeps sitting on same spot on top of the model, so it can't cool down and solidify. This is a limitation of this printing-concept.

 

I often print small models that have this problem. Then I print multiple at once, so one can cool while the other is printing. Or I print a dummy tower next to the real model. Ideally, the dummy should have the complementary surface area as the real model, so that the total area per layer is constant. Brutal changes in layer area show up as horizontal lines on small models.

 

Printing slow and cool also helps.

 

I am no fan of moving away the nozzle without extruding: then the filament keeps sitting in the nozzle for a longer time, and gets a different viscosity. This also shows up as horizontal deformations in the model. And the nozzle may leak while sitting and waiting aside, causing blobs.

 

A dummy tower reduces the effect, but does not eliminate it:

 

 

Theoretical model of a dummy with complementary shape:

 

 

Part of a real design:

 

 

Tiny models, each ca. 20mm high, printed at different speeds and temperatures. Printing tiny models on their back -if the model allows it - also increases layer cooling time:

 

This did help alot, but its still not as close as i would like it (still a bit of oozing than what should be on the tips). Ill try decreasing the temps a bit next since i set the setting back to default.

 

Thanks for the help gr5 and geert_2! You may see me around the forums more because i have a few other (minor) issues to debug. 🙂

[gr5 2,004]

well then maybe try two towers - on on either side.  When I printed really tiny people with a 0.25mm nozzle I had to print about 7 of them so each one cools quite a bit.

[Whayt 0]

12 hours ago, gr5 said:

well then maybe try two towers - on on either side.  When I printed really tiny people with a 0.25mm nozzle I had to print about 7 of them so each one cools quite a bit.

 I'll try that. I just also put a new nozzle on also that was in much better condition than the old one. (I didn't know it was that worn 😬).

[geert_2 556]

On 3/7/2020 at 12:52 AM, Whayt said:

...

Ill try decreasing the temps a bit next since i set the setting back to default.

...

 

Yes, you should definitely print cooler. On my UM2 the standard for PLA is 210°C, but for tiny models printed slowly and in thin layers, I can go down to 190°C.

 

On a test piece, while printing, try going down manually in steps of 5°C, and see what happens. At some point it will start to underextrude severely. Then go up a little bit until it flows well again. Then try that value for a whole tiny model.

 

[Whayt 0]

9 hours ago, geert_2 said:

 

Yes, you should definitely print cooler. On my UM2 the standard for PLA is 210°C, but for tiny models printed slowly and in thin layers, I can go down to 190°C.

 

On a test piece, while printing, try going down manually in steps of 5°C, and see what happens. At some point it will start to underextrude severely. Then go up a little bit until it flows well again. Then try that value for a whole tiny model.

 

 

Ill have to try that when i get the chance. Ive been running it at 195c but im also having issues with the extruder grinding the filament when the bed is level and the nozzle (seems) clear.